#include<iostream>
#include<cstring>
#include<string>
using namespace std;


double & add(double &d)
{
    d=d+3;
    return d;

}
int main()
{

    double d=42.;
    double &ref =d;

    cout<< ref++ <<endl;
    cout<< d << endl;

    cout << add(ref) << endl;
    cout << d << endl;

}
